Zinc deficiency causes retardation and, ultimately, cessation of growth in species of all phyla. We have shown that zinc is essential in general, for the progression of cells through the series of biologic events that define the cell cycle and, in particular, for many of the cellular components, enzymes and nucleic acids which participate in those biologic processes. Our present objective is to employ the eukaryotic organism, Euglena gracilis, strain Z, in order to define the steps in cell division which are critically affected by zinc deficiency and to identify the biochemical processes which become the limiting factor in those events. We will isolate the RNA polymerases, DNA, ribosomal, transfer and messenger RNA, ribosomes, and ribosomal proteins from zinc sufficient and deficient cells. We will determine the effect of zinc deficiency or its imbalance on the structure and function of these nucleic acids and their polymerases, as well as on the regulation of protein synthesis. Our long term goal remains the generalization of understanding to other organisms, so that we might define the mechanisms by which zinc deficiency, and/or imbalance, results, e.g., in congenital malformations and growth retardation in vertebrates, including man.